The present invention relates to an optical transmitter and receiver device for use in transmission and reception of optical signals in optical communication and data transmission systems, and in particular, to improvement of an optical module in the device.
A conventional optical transmitter and receiver device comprises two optical modules. One of them is an optical receiving module comprising a photodetector such as a photodiode and is connected to a receiver circuit to form an optical receiver. The photodetector converts an incoming optical data signal to an electrical reception signal and the receiver circuit decodes the electrical reception signal to produce a data signal representative of the incoming optical data signal.
The other is an optical transmitting module comprising a luminous element such as a laser diode and is connected to a transmitter circuit to form an optical transmitter. The transmitter circuit receives a transmitting data signal and drives the luminous element to make the luminous element emit an outgoing optical data signal representative of the transmitting data signal. The optical transmitting module often has a monitor photodetector for monitoring a power of the outgoing optical data signal to produce an electrical monitoring signal. The transmitter circuit receives the electrical monitoring signal and controls the luminous element to stabilize the emitting power of the luminous element.
Among various uses of such an optical transmitter and receiver device, is in a user's set connected to a subscriber optical line in an optical telecommunication system, or in a terminal equipment connected to a computer system through an optical cable.
The user's set and computer terminal equipment especially need to be small in size and low in cost. However, the conventional optical transmitter and receiver device unfortunately makes the user's set and computer terminal equipment large in size and high in cost, because it has two optical modules.